Bio-soluble inorganic fiber

ABSTRACT

Inorganic fibers including the following composition, SiO 2 , MgO and CaO being main components: SiO 2 : 73.6 wt % to 85.9 wt %, MgO: 9.0 wt % to 21.3 wt %, CaO: 5.1 wt % to 12.4 wt %, Al 2 O 3 : 0 wt % or more and less than 2.3 wt %, and Fe 2 O 3 : 0 wt % to 0.50 wt %.

TECHNICAL FIELD

The invention relates to bio-soluble inorganic fibers.

BACKGROUND ART

Asbestos have been used as a heat-resistant sealing material, forexample, since they are light in weight and have excellent heatresistance. However, use of asbestos is prohibited since it causesdisorders of lungs. Therefore, instead of asbestos, ceramic fibers orthe like have been used. It is thought that ceramic fibers or the likehave excellent heat resistance which is equivalent to that of asbestos,and no health problem may occur as long as they are handledappropriately. However, there is a trend that a higher degree of safetyis required. Under such circumstances, various bio-soluble fibers havebeen developed in order to realize bio-soluble fibers which do not causeor hardly causes health problems even if they are inhaled in a humanbody (see Patent Document 1, for example).

Like asbestos, conventional inorganic fibers are secondary processedinto a shaped product or an unshaped product together with variousbinders or additives, and are used as a joint in a heat treatingapparatus, a furnace such as an industrial furnace, an incinerator orthe like, a joint which fills the gap of refractory tiles, insulatingbricks, shell, refractory mortar or the like, a sealing material, apacking material, an insulating material, or the like. In many cases,the inorganic fibers in use are exposed to high temperatures, and theyare required to have heat resistance.

Further, in many cases, alumina is used in a member of a furnace. Therewas a problem that fibers contained in a secondary-processed productreact with the alumina, thereby causing the secondary product or themember to adhere and melt.

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: JP-A-2012-148947

SUMMARY OF THE INVENTION

An object of the invention is to provide inorganic fibers havingexcellent bio-solubility, heat resistance and alumina reactivityresistance.

According to the invention, the following inorganic fibers or the likeare provided.

1. Inorganic fibers comprising the following composition, SiO₂, MgO andCaO being main components:

-   -   SiO₂: 73.6 wt % to 85.9 wt %    -   MgO: 9.0 wt % to 15.0 wt %    -   CaO: 5.1 wt % to 12.4 wt %    -   Al₂O₃: 0 wt % or more and less than 2.3 wt %    -   Fe₂O₃: 0 wt % to 0.50 wt %    -   SrO: less than 0.1 wt %.

2. The inorganic fibers according to 1, which have the followingcomposition:

-   -   SiO₂: 74.0 wt % to 80.0 wt %    -   MgO: 9.0 wt % to 15.0 wt %    -   CaO: 5.1 wt % to 12.4 wt %    -   Al₂O₃: 0 wt % or more and less than 2.3 wt %    -   Fe₂O₃: 0 wt % to 0.50 wt %    -   SrO: less than 0.1 wt %.

3. The inorganic fibers according to 1 or 2, which comprise MgO in anamount of 9.0 wt % to 14.0 wt %.

4. The inorganic fibers according to any one of 1 to 3, which compriseAl₂O₃ in an amount of 0.17 wt % to 2.2 wt %.

5. The inorganic fibers according to any one of 1 to 4, which compriseZrO₂ in an amount of more than 0.1 wt % and 10.9 wt % or less. 6. Theinorganic fibers according to any one of 1 to 5, which comprise TiO₂ inan amount of more than 0.1 wt % and 10.9 wt % or less. 7. The inorganicfibers according to any one of 1 to 6, which comprise alkali metal oxidein an amount of more than 0.01 mol % and less than 0.20 mol %. 8. Theinorganic fibers according to any one of 1 to 7, which comprise B₂O₃ inan amount of less than 0.1 wt %. 9. The inorganic fibers according toany one of 1 to 8, wherein the total of the amounts of SiO₂, MgO and CaOis 90.0 wt % or more.

10. The inorganic fibers according to any one of 1 to 9, wherein thetotal of the amounts of SiO₂, MgO and CaO is 93.0 wt % or more. 11. Theinorganic fibers according to any one of 1 to 10, wherein the total ofthe amounts of SiO₂, MgO and CaO is 96.0 wt % or more. 12. A secondaryproduct or composite material produced by using the inorganic fibersaccording to any one of 1 to 11.

According to the invention, it is possible to provide inorganic fibershaving excellent bio-solubility, heat resistance and alumina reactivityresistance.

MODE FOR CARRYING OUT THE INVENTION

The inorganic fibers of the invention comprises the followingcomposition, wherein SiO₂, MgO and CaO are main components:

-   -   SiO₂: 73.6 wt % to 85.9 wt %    -   MgO: 9.0 wt % to 21.3 wt %    -   CaO: 5.1 wt % to 12.4 wt %    -   Al₂O₃: 0 wt % or more and less than 2.3 wt %    -   Fe₂O₃: 0 wt % to 0.50 wt %.

The main components mean that, among all the components contained in theinorganic fibers, the three components of which the contents (wt %) arethe highest, i.e. the component which is firstly high in content, thecomponent which is secondary high in content, and the component which isthirdly high in content, are SiO₂, MgO and CaO.

In this specification, “∘wt % to Δwt %” means “∘wt % or more and Δwt %or less”.

In respect of heat resistance, the main three components preferably havethe following composition:

-   -   SiO₂: 74.0 wt % to 80.0 wt %    -   MgO: 9.0 wt % to 18.0 wt %    -   CaO: 5.1 wt % to 12.4 wt %.

More preferably, the main three components have the followingcomposition:

-   -   SiO₂: 74.2 wt % to 78.4 wt %    -   MgO: 9.7 wt % to 16.1 wt %    -   CaO: 5.2 wt % to 12.2 wt %.

In the inorganic fibers of the invention, the lower limit of the amountof SiO₂ can be 73.6 wt % or more, 73.7 wt % or more, 74.2 wt % or more,74.4 wt % or more, 75.0 wt % or more, or 75.8 wt % or more, for example.The upper limit of the amount of SiO₂ can be 85.9 wt % or less, 82.0 wt% or less, 81.0 wt % or less, 80.0 wt % or less, or 78.0 wt % or less,for example. These lower limits and these upper limits can be combinedarbitrarily.

In the inorganic fibers of the invention, the lower limit of the amountof MgO can be 9.0 wt % or more, 9.2 wt % or more, 9.4 wt % or more, 9.6wt % or more, 9.7 wt % or more, 10.0 wt % or more, 11.0 wt % or more, or11.8 wt % or more, for example. The upper limit of the amount of MgO canbe 21.3 wt % or less, 20.0 wt % or less, 18.0 wt % or less, 16.0 wt % orless, 15.0 wt % or less, 14.0 wt % or less, or 13.5 wt % or less, forexample. These lower limits and these upper limits can be combinedarbitrarily.

In the inorganic fibers of the invention, the lower limit of the amountof CaO can be 5.1 wt % or more, 5.9 wt % or more, 6.5 wt % or more, or7.7 wt % or more, for example. The upper limit of the amount of CaO maybe 12.4 wt % or less, 12.2 wt % or less, 11.2 wt % or less, or 10.2 wt %or less, for example. These lower limits and these upper limits can becombined arbitrarily.

The total of the amount of SiO₂, MgO and CaO may be 87.5 wt % or more,90.0 wt % or more, 92.0 wt % or more, 94.0 wt % or more, 96.0 wt % ormore, 98.0 wt % or more, 99.5 wt % or more, or 100.0 wt % (inevitableimpurities may be contained).

The remaining other than the above components is oxides of the otherelements, impurities or the like.

In the inorganic fibers of the invention, the lower limit of the amountof Fe₂O₃ can be 0.00 wt % or more, or more than 0.00 wt %, for example.The upper limit of the amount of Fe₂O₃ can be 0.60 wt % or less, 0.50 wt% or less, 0.40 wt % or less, 0.3 wt % or less, or 0.20 wt % or less,for example. When the amount of Fe₂O₃ is too much, the fibers may colorwith heat, or crystallization may be accelerated so that the strengthmay be lowered. Also, the heat resistance may be lowered. The lowerlimit and the upper limit can be combined arbitrarily.

In the inorganic fibers of the invention, the lower limit of the amountof Al₂O₃ can be 0.0 wt % or more, more than 0.0 wt %, 0.15 wt % or more,or 0.17 wt % or more, for example. The upper limit of the amount ofAl₂O₃ can be less than 2.3 wt %, 2.2 wt % or less, 2.0 wt % or less, 1.8wt % or less, 1.6 wt % or less, 1.5 wt % or less, 1.4 wt % or less, 1.3wt % or less, or 1.2 wt % or less, for example. These lower limits andthese upper limits can be combined arbitrarily.

TiO₂ and ZrO₂ may be contained or not may be contained, respectively.The respective lower limit of the amount thereof can be 0 wt % or more,0.1 wt % or more, 0.15 wt % or more, 0.5 wt % or more, 1.0 wt % or more,1.5 wt % or more, 2.0 wt % or more, or 2.5 wt % or more, for example.The respective upper limit of the amount thereof can be 12.4 wt % orless, 12.0 wt % or less, 10.0 wt % or less, 8.0 wt % or less, 6.0 wt %or less, 5.0 wt % or less, 3.0 wt % or less, 2.3 wt % or less, 2.0 wt %or less, 1.0 wt % or less, 0.5 wt % or less, less than 0.1 wt %, or 0.05wt % or less, for example. These lower limits and these upper limits canbe combined arbitrarily.

ZrO₂ is preferably contained in an amount of 0.5 wt % to 8.0 wt %, or3.0 wt % to 7.0 wt %, more preferably 3.5 wt % to 6.0 wt %. The lowerlimit of the amount of ZrO₂ can be 5.05 wt % or more, or 5.5 wt % ormore.

TiO₂ is preferably contained in an amount of 0.5 wt % to 8.0 wt %, morepreferably 1.0 wt % to 7.0 wt %.

The inorganic fibers of the invention can contain one or two or morecomponents selected from Al₂O₃, ZrO₂ and TiO₂ in the above-mentionedamounts.

The inorganic fibers preferably have the following composition, whereinSiO₂, MgO and CaO are main components:

-   -   SiO₂: 73.6 wt % to 85.9 wt %    -   MgO: 9.0 wt % to 21.3 wt %    -   CaO: 5.1 wt % to 12.4 wt %    -   Al₂O₃: less than 2.3 wt %    -   Fe₂O₃: 0 wt % to 0.50 wt %    -   ZrO₂: 0.00 wt % to 0.05 wt %.

The inorganic fibers preferably have the following composition, whereinSiO₂, MgO and CaO are main components:

-   -   SiO₂: 73.6 wt % to 85.9 wt %    -   MgO: 9.0 wt % to 21.3 wt %    -   CaO: 5.1 wt % to 12.4 wt %    -   Al₂O₃: less than 2.3 wt %    -   ZrO₂: 3.0 wt % to 7.0 wt %.

The inorganic fibers preferably have the following composition, whereinSiO₂, MgO and CaO are main components:

-   -   SiO₂: 73.6 wt % to 85.9 wt %    -   MgO: 9.0 wt % to 21.3 wt %    -   CaO: 5.1 wt % to 12.4 wt %    -   Al₂O₃: less than 2.3 wt %    -   ZrO₂: 0.0 wt % to 7.0 wt %    -   TiO₂: 0.5 wt % to 8.0 wt %.

The inorganic fibers of the invention may or may not contain an oxide ofan element selected from Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er,Tm, Yb, Lu and Y, or a mixture thereof. The oxides may be contained inan amount of 3.0 wt % or less, 2.0 wt % or less, 1.0 wt % or less, or0.5 wt % or less, respectively.

Each of alkaline metal oxides such as Na₂O, Li₂O and K₂O may or may notbe contained. The amount thereof can each or in total be 3 wt % or less,2 wt % or less, 1 wt % or less, 0.5 wt % or less, 0.4 wt % or less, 0.3wt % or less, 0.2 wt % or less, or 0.10 wt % or less.

Alternatively, the amount thereof may be more than 0.01 mol % and lessthan 0.20 mol %.

Each of ZnO, B₂O₃, P₂O₅, SrO, BaO and Cr₂O₃ may or may not contained.The amount thereof can each be 3.0 wt % or less, 2.0 wt % or less, 1.0wt % or less, 0.5 wt % or less, less than 0.1 wt %, or 0.05 wt % orless.

The amounts of respective components mentioned above may be combinedarbitrarily.

The inorganic fibers can be produced by a known method such as a meltingmethod or a sol-gel method. A melting method is preferably because ofthe low cost. In the melting method, fibers are prepared by preparing amelt of raw materials in the customary manner, and allowing the melt tobe fibrous. For example, fibers can be prepared by a spinning method inwhich a molten raw material is flown onto a wheel which is rotating at ahigh speed, or by a blowing method in which compressed air is applied toa molten raw material.

The average fiber diameter of the inorganic fibers of the invention isnormally 0.1 to 50 μm, preferably 0.5 to 20 μm, further preferably 1 to10 μm, and most preferably 1 to 8 μm. The average fiber diameter may beadjusted to be an intended value by a known production method such asthe number of rotation, acceleration, compressed air pressure, air flowvelocity, air flow amount or the like.

The inorganic fibers of the invention may or may not be subjected to aheat treatment.

If a heat treatment is conducted, the temperature may be a temperatureat which the fiber shape be retained. Since the physical properties ofthe fibers vary by the heating temperature and the heating time, thefibers may be treated appropriately such that desired performance (creepresistance, shrinkage, strength, elasticity) can be exhibited.

The inorganic fibers change from amorphous to crystalline by a certainheat treatment. As mentioned above, it suffices that desired performanceis exhibited. The inorganic fibers may be either amorphous orcrystalline, or may be a state in which an amorphous part and acrystalline part are mixed.

The heating temperature is preferably 600° C. or higher, or 800° C. orhigher, more preferably 1000° C. or higher, 1200° C. or higher, 1300° C.or higher, or 1400° C. or higher. The heat temperature is preferably ina range of 600° C. to 1400° C., more preferably 700° C. to 1200° C.,800° C. to 1200° C., 700° C. to 1000° C., or 800° C. to 1000° C.

By having the above-mentioned composition, the inorganic fibers of theinvention are dissolved in physiological saline having a pH of 7.4.Further, they have solubility even after heating (after crystallizing).

The dissolution velocity constant that is measured by the same method asused in Examples is preferably 100 ng/cm²·h or more, 150 ng/cm²·h ormore, 200 ng/cm²·h or more, 300 ng/cm²·h or more, 500 ng/cm²·h or more,or 1000 ng/cm²·h or more.

The inorganic fibers of the invention have low alumina reactivity.Preferably, the inorganic fibers do not react with alumina at least at1300° C. Not reacting with alumina means that, when evaluated by themethod as used in Examples, an alumina pellet does not adhere due tomelting to a fleece or a blanket made from the fiber, namely the stateother than that is evaluated as poor (x).

The heat shrinkage of the fiber, when measured by the method as used inExamples, is preferably 20% or less, more preferably 10% or less, themost preferably 5% or less, or 3% or less, with heating at 1200° C.,1300° C., 1350° C. or 1400° C. for 8 hours. It is preferably 10% or lesswith heating at 1300° C. for 100 hours.

The fibers of the invention are excellent in tensile strength. Thetensile strength of the fiber is preferably 45 kPa or higher measured bythe method as used in Examples.

Various secondary products can be obtained from the fibers of theinvention. For example, a shaped product such as bulk, blanket, block,rope, yarn, textile fabrics, fiber applied with a surfactant, shot-lessbulk in which shots (un-fibrous product) have been reduced or removed, aboard produced by using a solvent such as water, a mold, paper, felt,wet felt impregnated with colloidal silica, or the like can be obtained.Further, a shaped product obtained by treating these shaped productswith colloid or the like can be obtained. Further, an unshaped product(mastic, caster, coating material or the like) produced by using asolvent such as water can be obtained. In addition, a structural bodyobtained by combining the shaped product or the unshaped product, andvarious heaters can be obtained.

As specific applications of the fibers of the invention, a joint in aheat treating apparatus or a furnace such as an industrial furnace andan incinerator, a joint which fills the gap of refractory tiles,insulating bricks, shell, refractory mortar or the like, a sealingmaterial, a packing material, a cushion material, an insulatingmaterial, a refractory material, a fire proofing material, aheat-retention material, a protective material, a coating material, afiltering material, a filter material, an insulating material, a joint,a filler, a repairing material, a heat resistant material, anon-combustible material, a sound proof material, a sound absorbingmaterial, a friction material (an additive for brake pad, for example),a glass plate/steel plate conveying roll, an automobile catalyst carrierretaining material, various fiber-reinforced composite materials(reinforcing fibers for fiber-reinforced cement or fiber-reinforcedplastics, reinforcing fibers for a heat resistant material or arefractory material, and reinforcing fibers for an adhesive or a coatingmaterial, for example) can be given.

EXAMPLES Examples 1 to 80 and Comparative Examples 1 to 14

The fibers having the composition shown in Tables 1 and 2 were preparedby a melting method, and evaluated by the following methods. The resultsare shown in Tables 1 and 2. Blanks in the composition in the tablesmean that the content is below the detection limit (less than about 0.01wt %).

(Heat Resistance)

Heat shrinkage was measured as the evaluation of heat resistance of thefiber.

The heat shrinkage of the fiber was measured before and after heating atpredetermined temperatures between 1200° C. to 1400° C. for 8 hours or100 hours for a fleece or a blanket made from the fiber (a size of 150mm in length, 50 mm in width, and 5 to 50 mm in thickness).

Platinum pins were driven at two or more points on the surface of eachsample made, and the distance between the platinum pins was measuredbefore and after heating. The dimensional change was evaluated as theheat shrinkage.

(Alumina Reactivity Resistance)

About 1 g of alumina powder having purity of 99% or more waspress-molded by means of a mold having a diameter of 17 mm to obtain apellet. The pellet was placed on a fleece or blanket sample (50 mm×50mm, thickness: 5 to 50 mm) that was made from the fiber. The sample onwhich the pellet was placed was heated at 1300° C. for 8 hours toconfirm the reactivity after the heating. The sample which did not reactwith the pellet at all was evaluated as very good (⊚). The sample towhich the pellet adhered weakly (the pellet could be peeled off by hand,and the pellet and the sample were not molten by appearance) wasevaluated as good (∘). The sample which reacted with the pellet (thepellet and the sample were molten and adhered to each other) wasevaluated as poor (x).

(Bio-Solubility)

The bio-solubility of the unheated fibers and the fibers after heatingat 1300° C. for 8 hours were measured by the following method.

The fibers were placed on a membrane filter. On the fibers,physiological saline having a pH of 7.4 was added dropwise from a micropump. The filtrate which had passed through the fibers and the filterwas collected in a container. The collected filtrate was taken out afterthe passage of 24 hours. The eluent components were quantified by an ICPemission analyzer to calculate the solubility. The elements to bemeasured were three elements, i.e. Si, Mg and Ca, that were mainelements. The average fiber diameter was measured and the solubility wasconverted using the average fiber diameter to the dissolution rateconstant (unit: ng/cm²·h), which was the eluent amount per unit surfacearea·unit time.

(Average Fiber Diameter)

400 or more fibers were observed and photographed by an electronmicroscope. Thereafter, the diameter was measured for the photographedfibers, and the average value of all measured diameters was taken as theaverage fiber diameter.

(Tensile Strength)

The fiber was subjected to needling processing to produce a blanket. Atensile strength was measured by means of a universal tester. As theblanket, a sample having a density of about 128 kg/m³ and a size of 50mm in width and 25 mm in thickness was used. As for the testingconditions, both ends were fastened such that a span was 100 mm and atensile speed was 20 mm/min. The value of the maximum load under whichthe test sample was broken was taken as a tensile strength.

TABLE 1 Shrinkage after Solubility Alumina Average Shrinkage afterheating for 8 hours heating for 100 Solubility (after reactivity fiberTensile Composition (wt %) (%) hours (%) (unheated) heating) resistancediameter strength MgO CaO SiO2 Al2O3 Na2O K2O Fe2O3 MoO3 TiO2 ZrO2 1200°C. 1300° C. 1350° C. 1400° C. 1300° C. PH 7.4 PH 7.4 1300° C. 8 h (μm)(kPa) Example 1 19.2 5.2 74.0 1.23 0.11 0.10 0.17 0.01 2.0 5.6 13.5 18.51102 ◯ 3.7 Example 2 19.9 5.1 73.7 1.16 0.18 2.1 4.5 16.2 ◯ Example 310.6 12.2 76.1 0.90 0.15 0.05 5.2 Example 4 11.2 11.8 75.9 0.89 0.150.03 Example 5 11.4 11.2 76.4 0.85 0.15 0.02 3.8 4.3 Example 6 11.9 10.976.2 0.84 0.15 0.01 0.01 Example 7 12.6 10.2 75.8 0.87 0.04 0.14 2.1 2.13.1 15.7 3.2 870 126 ◯ 4.4 Example 8 13.2 9.7 76.0 0.96 0.14 3.2 Example9 13.9 8.7 76.3 0.88 0.16 2.1 3.0 4.1 17.6 4.7 ◯ Example 10 14.7 8.076.3 0.94 0.15 Example 11 15.2 7.3 76.4 0.91 0.05 0.15 2.9 2.5 5.4 12.15.2 ◯ Example 12 15.3 7.8 75.8 1.00 0.11 0.01 0.01 Example 13 16.1 7.175.7 0.93 0.15 0.01 0.01 2.9 3.0 6.1 14.5 6.1 972 144 ◯ 3.7 Example 1416.5 6.8 75.6 0.89 0.17 0.02 3.0 ◯ Example 15 13.9 10.7 74.2 0.95 0.170.01 1.9 ◯ Example 16 16.0 5.2 77.8 0.82 0.16 0.01 3.3 4.3 ◯ 4.4 Example17 15.1 5.9 78.0 0.84 0.13 0.01 3.0 4.5 ◯ 4.7 Example 18 14.5 6.5 77.90.88 0.14 0.01 2.2 2.8 3.7 5.3 2.5 ◯ 5.0 53.6 Example 19 14.0 7.0 77.91.01 0.14 0.01 2.0 2.2 3.9 5.3 2.3 ◯ 4.3 47.9 Example 20 11.8 9.5 77.60.90 0.16 0.01 2.1 1.8 5.8 7.4 2.3 1350 ◯ 5.6 61.0 Example 21 9.7 11.877.3 1.02 0.15 0.01 3.3 7.1 6.5 ◯ 4.4 58.2 Example 22 11.0 10.0 77.90.97 0.13 6.7 9.9 Example 23 11.2 9.7 77.9 1.06 0.17 4.6 8.8 ◯ Example24 11.5 9.2 78.1 1.06 0.14 6.2 7.7 Example 25 11.6 9.4 77.9 0.94 0.050.16 5.5 7.2 10.6 7.5 1323 167 ◯ 5.0 Example 26 12.5 8.3 78.1 1.01 0.133.9 7.1 ◯ 56.4 Example 27 13.7 7.1 78.1 0.96 0.12 5.3 6.3 ◯ 4.5 Example28 13.9 7.0 77.9 1.07 0.15 5.6 8.2 1424 165 ◯ 4.8 Example 29 14.2 6.678.1 0.96 0.16 8.5 7.9 ◯ Example 30 14.3 6.1 78.4 0.99 0.18 9.9 ◯ 4.2Example 31 13.4 8.6 76.8 0.90 0.15 4.7 5.8 ◯ Example 32 12.6 9.3 76.90.98 0.15 3.8 5.3 5.0 1288 ◯ 4.8 Example 33 12.6 9.6 76.6 0.95 0.18 4.05.2 ◯ 4.9 Example 34 12.7 9.3 76.7 1.05 0.15 1414 ◯ 4.9 Example 35 12.49.9 76.5 0.99 0.16 1253 ◯ 4.2 Example 36 12.8 9.6 76.3 1.14 0.17 1385 ◯3.6 Example 37 12.8 9.1 76.8 1.05 0.16 4.9 6.7 1422 ◯ 3.6 Example 3812.5 9.5 76.6 1.22 0.18 3.4 3.5 4.3 ◯ 4.0 Example 39 12.9 9.7 75.7 1.510.17 3.2 4.4 757 ◯ 4.3 Example 40 12.5 9.3 76.5 1.52 0.14 3.2 4.4 ◯ 4.370.1 Example 41 12.2 9.8 76.2 1.68 0.20 5.9 7.0 8.5 542 ◯ 4.1 59.5Example 42 12.5 9.4 76.7 1.19 0.15 1.8 2.0 3.4 ◯ 4.3 54.3 Example 4312.7 9.5 76.3 1.07 0.22 0.16 1.2 1.5 2.1 1307 ◯ 5.0 63.8 Example 44 12.17.3 75.0 0.17 0.12 5.08 1.1 4.8 4.9 ⊚ Example 45 11.6 7.0 76.4 0.39 0.104.30 0.7 4.3 ⊚ 2.9 Example 46 12.0 8.6 76.3 0.26 0.14 2.44 0.20 3.7 791◯ Example 47 11.4 8.1 76.1 0.23 0.14 3.68 0.28 6.4 ◯

TABLE 2 Alumina Shrinkage after Solubility reactivity Average Shrinkageafter heating for 8 hours heating for 100 Solubility (after resistancefiber Tensile Composition (wt %) (%) hours (%) (unheated) heating) 1300°C. diameter strength MgO CaO SiO2 Al2O3 Na2O K2O Fe2O3 MoO3 TiO2 ZrO21200° C. 1300° C. 1350° C. 1400° C. 1300° C. PH 7.4 PH 7.4 8 h (μm)(kPa) Example 48 11.3 8.0 75.5 0.31 0.14 4.60 0.25 6.0 ◯ Example 49 10.88.5 74.4 0.28 0.16 5.60 0.17 3.2 6.2 5.5 511 ◯ 5.6 Example 50 10.9 8.175.1 0.26 0.15 5.15 0.15 7.2 ◯ Example 51 11.5 8.9 75.3 0.28 0.14 3.610.16 4.6 ◯ Example 52 12.3 8.7 75.5 0.26 0.17 2.80 0.21 2.9 3.3 ◯Example 53 10.1 12.4 75.1 2.20 0.15 2.2 9.9 ◯ Example 54 12.4 9.7 76.90.85 0.15 0.01 2.0 2.1 6.9 8.8 2.5 1614 ◯ 3.7 Example 55 12.3 9.9 76.70.93 0.14 0.06 2.2 2.4 6.5 8.7 2.6 1818 ◯ 5.6 Example 56 12.4 10.3 75.80.94 0.05 0.13 0.25 2.9 3.3 ◯ Example 57 12.2 10.1 76.2 0.93 0.14 0.415.1 ◯ Example 58 12.5 10.1 75.7 1.06 0.12 0.49 3.1 5.2 ◯ 3.9 Example 5912.9 9.7 75.7 0.92 0.05 0.18 0.56 4.4 ◯ Example 60 12.3 10.5 75.1 0.970.16 0.89 4.9 ◯ Example 61 12.5 9.6 75.7 1.01 0.16 1.00 3.6 5.3 ◯Example 62 12.2 9.8 75.7 1.01 0.15 1.10 5.2 935 ◯ 3.4 Example 63 12.49.5 75.8 1.03 0.14 1.10 5.5 ◯ Example 64 12.3 9.6 75.8 0.97 0.14 1.149.8 ◯ Example 65 12.3 9.5 75.8 0.96 0.17 1.19 4.5 7.4 ◯ Example 66 12.59.1 75.9 1.13 0.18 0.14 1.10 5.1 7.4 ◯ Example 67 12.8 8.9 75.7 1.130.21 0.14 1.08 4.9 7.1 ◯ Example 68 12.8 9.5 75.3 0.76 0.23 0.16 1.225.6 7.3 ◯ Example 69 12.9 9.8 75.1 0.66 0.15 0.18 1.17 4.8 6.7 ◯ Example70 13.0 9.7 75.0 0.51 0.25 0.06 0.18 1.21 4.3 6.9 ◯ Example 71 12.6 9.675.8 0.51 0.15 0.16 1.20 3.2 5.1 ◯ 3.9 Example 72 12.8 9.9 75.2 0.400.22 0.16 1.24 3.0 5.3 ◯ Example 73 12.8 9.5 75.7 0.47 0.28 0.14 1.043.8 5.4 ◯ Example 74 13.0 10.1 75.1 0.60 0.25 0.16 0.80 4.8 8.2 ◯Example 75 12.8 9.6 76.1 0.71 0.15 0.15 0.50 2.2 2.4 ◯ Example 76 13.29.2 76.1 0.86 0.16 0.15 0.29 1.4 ◯ Example 77 12.8 10.2 75.5 0.83 0.270.17 0.19 2.7 ◯ Example 78 13.3 9.7 75.5 0.95 0.21 0.16 0.08 1.8 1.913.4 14.6 4.9 1457 ◯ 2.9 Example 79 12.9 10.2 75.4 0.91 0.26 0.05 0.150.08 2.1 1586 ◯ Example 80 13.1 9.9 75.5 1.00 0.25 0.16 0.06 1.2 1.511.6 13.6 3.5 1558 ◯ 3.6 Comp. Ex. 1 17.9 4.3 75.9 1.58 0.21 0.13 0.013.3 4.5 7.6 8.4 7.4 610 26 X 3.3 19.4 Comp. Ex. 2 0.4 25.0 71.9 2.330.10 0.19 0.01 2.2 3.0 11.7 21.8 6.4 330 1437 X 3.1 44.4 Comp. Ex. 3 0.243.6 34.05 0.20 22.0 1.5 2.2 2.9 3.1 2.7 8 ⊚ 2.8 74.2 Comp. Ex. 4 0.149.6 50.23 0.06 2.6 3.5 4.3 4.6 4.0 21 ⊚ 2.2 44.9 Comp. Ex. 5 0.6 26.270.7 1.52 0.79 0.09 0.8 2.6 9.1 23.9 3.6 280 1520 X 4.6 32.8 Comp. Ex. 60.7 27.4 69.0 1.66 0.86 0.30 0.04 1.4 7.3 13.6 12.7 X 4.8 39.7 Comp. Ex.7 16.7 8.9 73.0 1.21 0.17 0.01 0.01 2.3 X Comp. Ex. 8 14.2 11.1 73.41.08 0.07 0.19 1.7 2.4 X Comp. Ex. 9 12.5 13.6 72.6 1.00 0.06 0.20 0.011.7 2.2 12.7 10.1 650 X 3.0 Comp. Ex. 10 12.3 12.9 73.6 0.97 0.05 0.160.01 2.0 X Comp. Ex. 11 11.8 13.3 73.6 1.00 0.06 0.17 0.01 2.0 X Comp.Ex. 12 11.7 14.2 73.0 0.91 0.12 0.01 2.0 X Comp. Ex. 13 11.4 15.4 71.90.92 0.05 0.22 0.01 1.6 2.7 6.1 X Comp. Ex. 14 11.8 14.5 72.8 0.57 0.200.01 0.01 1.3 2.7 X

INDUSTRIAL APPLICABILITY

The inorganic fibers of the invention can be used for variousapplications as a heat insulating material or a substitute for asbestos.

Although only some exemplary embodiments and/or examples of thisinvention have been described in detail above, those skilled in the artwill readily appreciate that many modifications are possible in theexemplary embodiments and/or examples without materially departing fromthe novel teachings and advantages of this invention. Accordingly, allsuch modifications are intended to be included within the scope of thisinvention.

The documents described in the specification are incorporated herein byreference in its entirety.

1. Inorganic fibers comprising the following composition, SiO₂, MgO andCaO being main components: SiO₂: 73.6 wt % to 85.9 wt % MgO: 9.0 wt % to15.0 wt % CaO: 5.1 wt % to 12.4 wt % Al₂O₃: 0 wt % or more and less than2.3 wt % Fe₂O₃: 0 wt % to 0.50 wt % SrO: less than 0.1 wt %.
 2. Theinorganic fibers according to claim 1, which comprise the followingcomposition: SiO₂: 74.0 wt % to 80.0 wt % MgO: 9.0 wt % to 15.0 wt %CaO: 5.1 wt % to 12.4 wt % Al₂O₃: 0 wt % or more and less than 2.3 wt %Fe₂O₃: 0 wt % to 0.50 wt % SrO: less than 0.1 wt %.
 3. The inorganicfibers according to claim 1, which comprise MgO in an amount of 9.0 wt %to 14.0 wt %.
 4. The inorganic fibers according to claim 1, whichcomprise Al₂O₃ in an amount of 0.17 wt % to 2.2 wt %.
 5. The inorganicfibers according to claim 1, which comprise ZrO₂ in an amount of morethan 0.1 wt % and 10.9 wt % or less.
 6. The inorganic fibers accordingto claim 1, which comprise TiO₂ in an amount of more than 0.1 wt % and10.9 wt % or less.
 7. The inorganic fibers according to claim 1, whichcomprise alkali metal oxide in an amount of more than 0.01 mol % andless than 0.20 mol %.
 8. The inorganic fibers according to claim 1,which comprise B₂O₃ in an amount of less than 0.1 wt %.
 9. The inorganicfibers according to claim 1, wherein the total of the amounts of SiO₂,MgO and CaO is 90.0 wt % or more.
 10. The inorganic fibers according toclaim 1, wherein the total of the amounts of SiO₂, MgO and CaO is 93.0wt % or more.
 11. The inorganic fibers according to claim 1, wherein thetotal of the amounts of SiO₂, MgO and CaO is 96.0 wt % or more.
 12. Asecondary product or composite material produced by using the inorganicfibers according to claim 1.